21981255 has 16 divisors (see below), whose sum is σ = 37239264. Its totient is φ = 11033600.

The previous prime is 21981251. The next prime is 21981283. The reversal of 21981255 is 55218912.

It is not a de Polignac number, because 21981255 - 2² = 21981251 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42846 + ... + 43355.

It is an arithmetic number, because the mean of its divisors is an integer number (2327454).

Almost surely, 2^21981255 is an apocalyptic number.

21981255 is a deficient number, since it is larger than the sum of its proper divisors (15258009).

21981255 is a wasteful number, since it uses less digits than its factorization.

21981255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86226.

The product of its digits is 7200, while the sum is 33.

The square root of 21981255 is about 4688.4171102836. The cubic root of 21981255 is about 280.1243282898.

The spelling of 21981255 in words is "twenty-one million, nine hundred eighty-one thousand, two hundred fifty-five".